This invention relates to novel photographic processes, elements and physical developer solutions. In a particular aspect it relates to photographic elements containing photosensitive palladium compounds and to processes for the formation of phthalocyanine dye images.
A wide variety of non-silver imaging processes are known in the photographic art. These are, however, generally unit quantum processes and therefore have low speed. High speed photographic processes such as conventional silver halide processes generally use an amplification step. This amplification step is generally autocatalytic in nature.
Processes for the formation of phthalocyanine dye images are known. For example, U.S. Pat. No. 2,915,392 issued Dec. 1, 1959 to Pederson describes a process whereby light activatable reducing agents (photoreductants) are used to reduce leucophthalocyanine dye thereby forming a phthalocyanine dye image. The process of Pederson, however, is necessarily a unit quantum process, that is, one mole of reducing agent must be light activated to obtain one mole of phthalocyanine dye. This results in an inherently slow process requiring long exposure times.
It is known that palladium complexes can be used to form latent image centers for the catalytic deposition of heavy metals from physical developer solutions. This type of process is described for example in Yudelson and Gysling U.S. Pat. No. 3,719,490; Yudelson and Dernbach U.S. Pat. Nos. 3,598,587; and Yudelson and Dernbach U.S. Pat. No. 3,650,748. While these systems are useful, many metals such as silver, copper, and palladium are extremely expensive and it is often desirable to have essentially non-metallic dye images which require no subsequent fix or stabilization steps.
The process of preparing visible metal images from palladium latent images has several disadvantages. These include (1) a relatively slow rate of development, (2) a complexing agent is required in the physical developer and (3) relatively high coverages of expensive palladium complexes are required.